Manufacture of vegetable parchment paper



April 28, 1970 K. AGAHD ETAL 3,508,859

MANUFACTURE 0F VEGETABLE PARGHMENT PAPER Filed Nov. 2, 1966 2 Sheets-Sheet 1 Apri 28, 1970 K. AGAHD ETAL 3,5 59

MANUFACTURE oF VEGETABLE PARCHMENT PAPER Filed Nov. 2, lees 2 Sheets-sheet a Reserva/'r /A/l/EA/TORS KONRAD AGAHD, MAX BAUER, voLKER DIETRICH, ADoLF H|LDENBRAND a WERNER ABELE Their ATTORNEYS United States Patent O 3,508,859 y MANUFACTURE OF VEGETABLE PARCHMENT PAPER Konrad Agahd, deceased, late of Kempten, Germany, by

Gerlinde Agahd, born Homola, heiress, Kempten, Germany; Max Bauer, Obergunzburg, Volker Dietrich, Durach, Adolf Hildenbrand, Kempten, and Werner Abele, Varel, Germany, assignors to Lever Brothers Company, New York, N.Y., a corporation of Maine Coutinuation-in-part of application Ser. No. 189,344, Apr. 23, 1962. This application Nov. 2, 1966, Ser. No. 601,260

Int. Cl. D21h 5/08 U.S. 'CL 8-119 6 Claims ABSTRACT F THE DISCLOSURE A process of manufacturing thin parchment paper Where a paper web is treated with parchmentizing liquids from a storage reservoir while the web is supported in a substantially tensionless condition on a train of driven rollers, the rollers having an adhesion-resistant peripheral surface of a material such as polyethylene, polytetrauoroethylene and silicone rubber. The web is thereafter dried.

This application is a continuation-in-part of U.S. application Ser. No. 189,344 filed Apr. 23, 1962.

This invention relates to the manufacturing of vegetable parchment paper and more particularly concerns the provision of an improved process and apparatus for such manufacture.

The manufacture of vegetable parchment paper is based on the conversion of the surface of the cellulose fibres of a paper into a colloid called amyloid. For this conversion of the cellulose fibres, apart from zinc chloride, use is made preferably of sulphuric acid. The film of gelatinous, water-insoluble amyloid produced on the surface of the paper at the same time encloses the cellulose fibres not affected by the acid and binds and cements them together. When the parchmentising process is stopped, which is done by diluting the parchmentising liquid and washing out with water, which water may contain, if the parchmentising liquid is acid, some alkali as neutralizer, and `when the paper web thus treated has dried, the amyloid coating with the cellulose fibres embedded in it dries to a horny consistency. The finished product is vegetable parchment paper. As regards permeability by air and fat, its resistance to water and the fineness of its pores, it compares favourably with the paper serving as the starting material.

It is already known to apply the parchmentising liquid, for example sulphuric acid, to both sides, or to one side, of the paper. For parchmentising on both sides, the paper web, which passes through rollers to guide it but is other- Wise unsupported, is passed through a bath of sulphuric acid. Another method of applying the parchmentising liquid is by means of applicator rollers. This process is very suitable for applying the parchmentising liquid on only one side so that a paper parchmentised on only one side can thereby be produced.

In the usual parchmentising processes, in which sulphuric acid is made to act on the paper in a bath, a substantial excess of sulphuric acid, in a strength of, say, 65-70% by weight, is generally used. This excess acid, which is not required for the parchmentising proper, requires considerable quantities of diluent water for its recovery on the countercurrent principle, so that comparatively large quantities of this dilute acid have to be concentrated in order to recover the excess acid. When the parchmentising acid is applied by means of applicator Patented Apr. 28, 1970 rollers this disadvantage is avoided, as the amount of sulphuric acid applied can be controlled lwithin certain limits by altering the gap between the applicator rollers.

During the parchmentising process the paper web cornes into contact with a great deal of water. In the wet state it loses the greater part of its dry strength and is therefore very susceptible to mechanical stress. It is consequently exposed in a very high degree to the risk of tearing or splitting when, carrying the load of the liquid adhering to it, it is pulled through the parchmentising apparatus. Tearing, and the associated splitting of the web, mean tiresome breakdowns in a continuous manufacturing process. The thinner the paper the greater the risk of tearing. The weight per square meter of the paper to be parchmentised cannot therefore be reduced at will. In order to counter this risk it is also necessary to run the paper web through the parchmentising apparatus at a comparatively slow speed, as at higher speeds there is the additional risk of the wet paper web looping around conveyor cylinders and again tearing. However, the extent to which the passage of the web can be slowed down is limited by economic factors and also by the fact that there may be a risk of excessive parchmentising action occurring if the paper is passed through the apparatus too slowly.

Finally, particularly when a thin paper is parchmentised, sticking of the amyloid coating of the parchmentised paper webs to rubber-coated or solid rubber cylinders or guide belts may cause the dreaded plucking that is to say the tearing out of fibres or Whole sections from the surface of the parchmentised layer with the undesirable formation of pore breakdowns in such layer. This plucking increases as the square of the increased in the speed of the machine. Since the risk of tearing or splitting increases as the weight per square meter of the paper decreases, it has so far only been possible to parchmentise at a more or less economic speed papers with weights of at least 35-40 grams per square meter.

It is an object of the present invention to provide a process and apparatus for manufacturing vegetable parchment paper in which the above disadvantages are mitigated or obviated. In particular the process and apparatus of the invention makes it possible to manufacture parchment paper having a uniform, poreless surface from paper webs having a weight of less than 30 grams per square meter, more especially from those of 2O to 25 grams per square meter in weight. Furthermore, by the process and apparatus of the invention it is possible to accurately regulate the degree of parchmentising, to effect good economy in the use of the parchmentising fluid and to increase the working speed.

According to the invention there is provided a process of manufacturing vegetable parchment paper by passing a web of parchmentisable paper over rollers while treating the web with parchmentising liquids followed by rinsing and drying, such process comprising the steps of conveying the web in substantially tensionless condition while providing continuous support for the web at least throughout its treatment with parchmentising and rinsing liquids, by providing a chain of driven rollers each of one meter minimum diameter which rotate at substantially equal peripheral speeds in line contact one with another, and by passing the web successively over each roller in the train in an arc of 260 to 280 about the roller and between each pair of adjacent rollers with opposite faces of the web in engagement with the surfaces of any two adjacent rollers, the maximum pressure between any two adjacent rollers being 0.5 kilogram per square centimeter.

Preferably the rollers have acid-resistant surfaces made of a material, for example a plastics material, to which the amyloid surface of the parchmentised paper web has little tendency to stick. Materials which have been found suitable for this purpose are polyethylene, polytetrailuoroethylene or silicone rubber. Previously parchmentising rollers have been given acid-resistant surfaces, preferably of rubber, as protection against the effect of sulphuric acid. Surprisingly, it has now been found that the adhesive force which holds the wet amyloid surface of the paper web t the surface of the rollers is greater in the case of rubber surfaces than in the case of those made of suitable plastics such as polyethylene, polytetrauoroethylene, and silicone rubber.

The parchmentisable paper web may have a weight of 20 to less than 30 grams per square meter, and be conveyed at feed rates of the order of 200 meters per minute. The preferred weight of web is 2O to 25 grams per square meter.

The invention will now be described with reference to the accompanying diagrammatic drawing which shows a side view of one form of apparatus for carrying out the process of the invention.

A parchmentisable paper web 2 coming from a reel 1 passes into the gap between a roller 3 and a roller 4 which, like all rollers in the parchmentising apparatus illustrated, have a surface of a plastics material, for example polyethylene. At the same time the paper web is pressed against the roller 3 by the pressure roller 4, the pressure of which can be regulated. In the gap 5 formed between the moving paper web 2 and the surface of the roller 3 where the web 2 contacts the roller 3, a storage reservoir 6 of parchmentising uid, for example sulphuric acid, is maintained, and constantly replenished as used. From this reservoir 6 the upper side of the paper web is charged with sulphuric acid. The amount of sulphuric acid applied and thus the degree of parchmentisation can be controlled by adjustment of the force with which the roller 4 is pressed against the roller 3, while at the same time the paper web can be compressed as desired by this pressure. Moreover the amount of sulphuric acid applied can also be regulated by changing the level of the reservoir 6.

If paper is to be parchmentised on both sides the pressure roller 4 is followed at a given distance by a second roller 7, the pressure of which can be regulated, another storage reservoir 9 of sulphuric acid being maintained in the gap 8 formed between the moving paper web 2 and the surface of the pressure roller 7. From this reservoir 9 the second side, i.e. the under side of the paper web 2, is wetted with parchmentising uid. If it is desired at any time to parchmentise only the upper side or only the under side of the paper web, in the former case the pressure of roller 7 and in the latter the pressure of roller 4 if relaxed, so that after the ilow of sulphuric acid to these points has been cut oi no storage reservoir is formed and thus no sulphuric acid is applied and parchmentising is not effected.

The paper web then passes over a train of horizontal rollers 3a, 3b, 3c, 3k which are identical with the rst roller 3. These rollers are arranged in two horizontal rows one above the other in such a way that the planes in which the axes of two of the contacting rollers lie, arranged one behind the other in a zig-zag line, are inclined at an angle of about 45 to the horizontal. The paper web 2, in passing over this train of rollers, travels alternately from top to bottom and from bottom to top, i.e. descending and ascending, and passes successively over each roller in the train in an arc of 260 to 280 about each roller and between each pair of adjacent rollers with opposite faces of the web in engagement with the surfaces of any two adjacent rollers, each of the rollers 3, 3a 3k having a minimum diameter of 1 meter. Each of the lower rollers 3, 3b, 3d, 3k is rigidly mounted, whereas each upper rollers 3a, 3c, 3e, 31' is adjustable vertically by means of slide supports (not shown) having adjustable pressure springs, in such a way that each upper roller makes line contact simultaneously with the lower preceding roller and the lower following roller, either without any pressure or at an adjustable pressure not exceeding 0.5 kilogram per square centimeter. Each roller has its own individual variable drive, and all the rollers 3, 3a, 3b, 3k are driven at substantially equal peripheral speeds. In this way the paper web is taken over the rotating rollers of the parchmentising apparatus without tension or stress and is never at any point without support.

The acid containing paper web 2 passes through one, or, if it is being parchmentised on both sides, through two equalising devices consisting of one or two friction cylinders 10, 10a the pressure of which can be regulated and which are driven at a peripheral speed different from that of the respective rollers 3a, 3b (either faster or slower) so that they have a smoothing action and have the effect of closing the pores on the surface of the amyloid coating.

After the paper web has left the equalising device of devices 10, 10a the parchmentising process is stopped by applying dilute acid from recovery baths 11, 11a, 11b of graduated concentration and then washing water which may contain alkali, preferably ammonia, in order to neutralise the last traces of acid. The dilute acid from the baths 11, 11a, 11b is sprayed on to the surface of the paper web at several places as it passes over the rollers 3c, 3d, 3e and 3f by a number of spray tubes 12, 12a, 12b, 12C which extend over the whole width of the paper web, so that one or if necessary both surfaces are treated. The washing water can be applied in the same way through the spray tubes 13, 13a, 13b 13e. After thorough washing the parchmentised paper then leaves the parchmentising apparatus and is dried in the usual way in a drying section 14.

Parchment paper made in accordance with the above process is distinguished by a marked absence of pore breakdowns due to plucking and even in the thinnest paper by an unbroken parchment coating and therefore has a particularly high resistance to grease. By this process papers having what has hitherto been regarded as an inadmissibly low weight of down to 2O grams per square meter can be processed to make parchment paper. As the wet paper web rests on the rollers 3a 3k without tension and stress and is at no point unsupported during its progress through the parchmentising device, the risk of tearing the wet paper web is practically eliminated.

The following two examples contrast the prior art production of vegetable parchment paper with the production of vegetable parchment paper according to the present invention.

PRIOR AiRT METHOD A parchmentisable paper web of width 226 millimeters and of weight 38 grams per square meter, and consisting of an unsized cellulose paper, is fed at a speed of 125 meters per minute from a discharge roll over a pair of feed-in cylinders, without support, into a parchmentising acid bath containing sulphuric acid of 60 to 70% concentration, over a guide roller in this bath through a looping angle of to 100, through an acid press having a roller diameter of 300 millimeters, and thence into a rst dilute acid bath. The distance from the entry of the web into the parchmentising acid bath to the entry into the first dilute acid bath is approximately 3 meters. When the web enters the first dilute acid bath the parchmentising process is stopped, because the acid concentration in this dilute acid bath is about 40%. The web is then conveyed through seven more dilute acid baths with acid concentrations reducing from 40% to 15%, and then the web is washed out in a washing section and finally neutralised, dried and reeled.

In this conventional process, the web is conveyed without support from the entry into the parchmentising acid baths to the entry into the iirst dilute acid bath, and is subject to considerable lengthwise tensions which give rise to frequent splits in the web. The number of splits,

particularly in the parchmentising acid stage, averaged one split to two tons of vfinished parchment paper. A machine stoppage occurred with every split. The number of splits is the deciding factor for not producing a parchment paper weighing less than 40 grams per square millimeter by the prior art process, since the number of splits rises sharply as the weight of the paper is reduced below 40 grams per square meter. Splits can only be avoided in the prior art process, to some extent, by drastic reduction of the web speed, but the greater the reduction of web speed the more uneconomic is the process.

Of great importance for grease resistance of the parchment paper is its lack of pore breakdowns. In the prior art process, the number of pore breakdowns increases with reduction of the weight of the web below 40 grams per square meter. Measured in breakdowns per square decimeter at the usual operating speed of 125 meters per minute, the web of 38 grams per square millimeter Weight averaged 15 pore breakdowns per square decimeter. When an attempt was made to speed up production by increasing the machine speed to 150 meters per minute, there was a considerable increase in the number of pore breakdowns to 70 per square decimeter, which meant that this material could no longer be used as a wrapper web for fats such as margarine.

PROCESS ACCORDING TO THE INVENTION A web of unsized parchmentisable cellulose paper 226 millimeters wide and of weight 38 grams per square meter was fed from a discharge reel at a speed of 170 meters per minute, into the nip between the pressure roller and the first roller of the horizontal train of rollers. The pressure roller diameter was 400 meters and the rollers in the train were each of diameter 1 meter, the planes in which the axes of any two of the rollers in the train, arranged one behind the other in a zig zag line were inclined at an angle of about 45 to the horizontal so that the web passed successively over each roller in the train in an arc of 270 about the roller. Each roller had an acid-resistant and adhesion-resistant surface of plastics material.

To the nip formed by the pressure roller and the first roller in the train sulphuric acid was applied to the web in a concentration of 60 to 70%, an acid storage reservoir being formed in the nip which was constantly replenished. The web, in its wet unstable condition passed through the parchmentising apparatus supported continuously in substantially tensionless condition by the train of rollers and was parchmentized, washed out in the washing section, neutralised, dried and reeled.

The `finished parchment paper was 210 millimeters wide and had a weight of 40 grams per square meter. At the machine speed of 170 meters per minute the number of splits in the web was one split per tons of iinished paper, and the pore breakdowns were reduced to 5 per square meter.

The consumption of sulphuric acid was reduced by 25% in comparison with the prior art process.

The process according to the invention was also used to produce a thin parchment paper with a weight of 20 grams per square meter, a paper which could not possibly be produced by the process according to the prior art.

The process according to the invention is particularly economical because it permits of an increased working speed of up to 200 meters per minute, and also because the consumption of parchmentising iiuid, for example sulphuric acid, is kept low. If the process is used as described for the treatment of paper on only one side, with a suitable setting of the cylinders 3 and 4, a parchment paper is obtained which has on one side a coating which is completely free of pores and greaseproof, whilst on the other, surprisingly, there has also been a certain cementing of the cellulose fibres, so that this side is sufli ciently resistant to friction although the surface qualities required, say, for printing or other finishes are not appreciably affected. The non-parchmentised side of paper parch-rnentised on one side is suitable for coating with plastics, which can be firmly attached. Paper, aluminium or plastic foils can be used to back the non-parchmentised side and adhere well. Finally, it is also possible, if necessary after suitable prior treatment, to vacuum-deposit metals on the non-parchmentized side of the paper web.

We claim:

1. In a process for manufacturing vegetable parchment paper by passing a web of parchmentisable paper over rollers while treating the web with parchmentising liquids from a storage reservoir at a nip, followed by rinsing with water sprays and drying, the steps of conveying the web in substantially tensionless condition While providing continuous support for the web at least throughout its treatment with parchmentising and rinsing liquids by providing a train of driven rollers suspended out of contact with a large liquid mass each of one meter minimum diameter which rotate at substantially equal peripheral speeds in line contact one with another, the rollers having an adhesion-resistant peripheral surface of a material selected from the group consisting of polyethylene, polytetrafluoroethylene and silicone rubber, and by passing the web successively over each roller in the train in an arc of 260 to 280 about the roller and between each pair of adjacent rollers with opposite faces of the web in engagement with the surfaces of any two adjacent rollers, the maximum pressure between any two adjacent rollers being 0.5 kilogram per square centimeter.

2. The process according to claim 1, wherein each roller in the train has an adhesion-resistant peripheral surface of polyethylene.

3. The process according to claim 1, wherein each roller in the train has an adhesion-resistant peripheral surface of polytetrauoroethylene.

4. The process according to claim 1, wherein each roller in the train has an adhesion-resistant peripheral surface of silicone rubber.

5. The process according to claim 1, wherein the web has a weight of 20 to less than 30 grams per square meter and the web is conveyed at feed rates of the order of 200 meters per minute.

6. The process according to claim 1, wherein the web has a weight of 20 to 25 grams per square meter and the web is conveyed at feed rates of the order of 200 meters per minute.

References Cited UNITED STATES PATENTS 1,548,261 8/1925 Franz 8-7 2,562,457 7/1951 Hannay et al.

500,915 7/1893 Leonhard 68-62 1,791,248 2/1931 Schwartz 8-119 XR 1,350,685 8/1920 Taylor 8-119 1,683,470 9/1928 Knops 8-119 2,665,660 1/1954 Olden 118-122 2,556,772 6/1951 Newlove 118-122 FOREIGN PATENTS 251,126 4/ 1926 Great Britain.

484,991 5 193 8 Great Britain.

OTHER REFERENCES American Dyestuf Reporter, Dennett, Dec. 15, 1947, pp. 748-753.

Chemical Abstract, vol. 49, 1955, col. 16434d, Marsh, Introduction to Textile Finishing, p. 35 & 52-54, pub. 1948 by Chapman & Hall.

DONALD LEVY, Primary Examiner 

